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A rocky weekend weather start – with a good finish

A rocky weekend weather start – with a good finish

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Buffalo Creek

Katheryn Gill, 7, left, and Evelyn Pollak, 7, collect minnows from Buffalo Creek at the Burchfield Nature & Art Center in Cheektowaga, on Friday, June 26, 2020.

There is risky business in this article, being composed on Friday morning. I’m writing about a limited severe weather threat posed by a small convective system which does not yet exist. A first system, producing intense to severe convection near northern Illinois, will slip south of Western New York, and is unlikely to impact our region. You can click on the lower right arrow to animate the radar.

It is a second wave which is expected to develop into what is called a mesoscale (smaller scale) convective system, or mcs, which may pose a threat to part or all of WNY much later tonight, toward the predawn and early morning hours of Saturday. The upper-level winds will propel this mcs toward the east-southeast. Determining the track of such systems before they even exist is the riskiest part. They often sink farther south than models indicate, but sometimes they do the opposite — which would pose more of a threat to the Niagara Frontier. With this in mind, the Storm Prediction Center has currently kept the 15% risk of severe thunderstorms with damaging winds and hail south of the metro area, and the lower 5% risk covering the larger portion of Western New York.

The greater enhanced risk is well to our west and southwest, closer to where the Friday morning convection has been found. Even if Western New York takes a hit early Saturday, the mcs pathway will be sinking southward toward Pennsylvania and the middle Atlantic region. Any risk of severe weather in Western New York during the day is more likely south of the metro area, as forecast by SPC, although somewhat tamer convection is still likely to the north.

We can examine what high-resolution models are currently projecting. One model shows a hit on the Niagara Frontier, around 4 a.m. Another high-resolution model brings the focal point of the mcs much farther south. Still another model puts a 3-4 a.m. hit near the Pennsylvania line, but brings another complex to the Niagara Frontier around 7 a.m.

Whatever the track of the mcs, it will also carry the risk of localized flooding because of very high amounts of water vapor which will be overhead, as seen in this water vapor imagery.

The precipitation amounts would be more manageable if spread out over a 24-hour period. However, the duration of this event will be shorter, obviously meaning potential downpours may overwhelm some storm drains in some locations. Here is some model output on rainfall totals.

The overall perspective is some parts of Western New York will probably experience some downpours and gusty winds, but the risk of truly severe storms with damaging winds is far more uncertain. For now, I give a small edge to rainfall and wind impacts being greater south of the metro area. Obviously, humidity will run up high before and during Saturday after a terrific Friday. The need for rainfall has been somewhat reduced since more widespread showers and thunderstorms occurred earlier in the week. Soil moisture change since May 31 still shows typical June drying, but less than had been showing last weekend.

After this Saturday system, however, rainfall potential will be low starting Sunday through the following week, meaning if the system fizzles, watering needs will build as the week goes along into July. Rainfall for Buffalo in June is running more than half an inch below average, but the deficit is smaller to the south and east where more downpours occurred earlier in the week.

Saturday night will remain humid, with a few more showers and thundershowers still possible, especially early in the evening. Sunday looks partly to mostly sunny with just moderate humidity, noticeably lower. The high should be close to 80, a little cooler near the immediate lakeshores, with only a light wind. Boaters will have an easier time of it (Saturday boating will be ill-advised, to say the least). Sunday wave heights will average 2 feet or less, with a west breeze shifting to northwest at around 10 knots.

Warmth in the early part of the week will bring highs in the low to mid-80s. Heat will build later in the week, as readings head closer to near 90 by the end of the week.

Fortunately, the circulation near a ridge of high pressure, while very warm, does not favor oppressive humidity to go with the warmth and heat. In the longer term, ensemble mean guidance continues to favor warmer than average temperatures dominating most days – but not every day – from Monday out to about 14 days. The Climate Prediction Center continues to show higher probabilities for such warmth through the eight- to 14-day period, and I agree.

The area favoring below average temperatures to the south is due to expected widespread convection, rather than the plume of Saharan dust some of you have seen in the news lately from the strong easterlies aloft carrying the dust across the Atlantic to the Caribbean and, eventually, the southeast U.S.

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